1. Field of the Disclosure
The present disclosure relates generally to energy, and, more particularly, to a power source capable of providing electricity in remote locations. In particular, the present application relates to an energy unit that provides safe and stable storage of hydrogen for use in making electricity.
2. Description of the Related Art
Producing electricity from hydrogen is known. In known applications, an electrolyzer is used for producing a source of hydrogen from water. As known in the art, hydrogen and oxygen are produced by electrolysis of water. A water electrolysis reaction occurs when sufficient energy is applied to break the water's oxygen-hydrogen-bond.
As known in the art, electrolysis includes an electrochemical process involving the decomposition of an electrolyte. During electrolysis, an electrolyte decomposes, for example, when an external DC voltage is applied to two electrodes, i.e., an anode and a cathode, which are in contact with the electrolyte. The voltage equals or exceeds a threshold value, which, depending upon the particular electrolyte, causes the electrolyte to decompose and the hydrogen-water bond to break. The minimum voltage necessary to decompose the electrolyte is referred to as the “decomposition voltage.” Water may also be electrolyzed using other processes, such as a photosynthetic process, for example.
Furthermore and as known in the art, some proton exchange-membrane (“PEM”) electrolyzers enable the production of hydrogen and oxygen through the electrolysis of water. PEM electrolyzers include electrolyte material, which includes a proton-conducting polymer membrane. When the membrane becomes wet, sulfonic acid attached thereto detaches, and the membrane becomes acidic and proton-conducting. Protons, i.e., positively charged hydrogen ions, pass through the membrane, while anions, i.e., negatively charged ions, do not pass through the membrane.
Thus and as known in the art, PEM electrolyzers separate pure water into hydrogen and oxygen when a DC voltage is applied to electrodes (i.e., cathode and anode) provided with the PEM electrolyzers. When the DC voltage exceeds the decomposition voltage, the electrolyzer splits pure water into hydrogen and oxygen. Other techniques for separating water into hydrogen and oxygen are known. Also and as known in the art, fuel cell technology allows the use of hydrogen as fuel to produce electricity. For example, hydrogen collected as a function of PEM electrolyzers is used in fuel cells. Moreover, several individual fuel cells are combinable in a unit, referred to in the art as a “fuel cell stack.” A fuel cell stack is desirable to achieve an appreciable output voltage and/or current. Thus, in order to achieve appreciable output voltages, several individual fuel cells must be combined in a unit called a fuel cell stack.
Adjacent fuel cells can be connected by a separator, which may be formed as a plate. The plate is operable to provide electrical connections between the respective fuel cells. Also, the plates can provide a gas transport towards and away from the respective fuel cells. Further heat that is produced by the respective fuel cells can be dissipated by the separator plate. Moreover, adjacent cells can be sealed by the separator plate, thereby preventing fuel and oxidant leakage.
In some known embodiments, plates are attached to the ends of a fuel cell stack. The plates are operable to electrically connect one or more external circuits and can also provide connections for gas flow. Due to production of heat, one or more fuel stack may be further provided with cooling, including by air or water.
In known hydrogen-based fuel cells, electrical production occurs as a function of hydrogen atoms contacting the plate, effectively taking electrons from the hydrogen atoms and producing free electrons. Hydrogen generally exists in nature as di-hydrogen (H2) molecules. Every two di-hydrogen molecules (2H2) include 4 hydrogen protons and 4 free electrons of potential energy (4H++4e−). Further and as known, oxygen atoms are attracted to the positively charged hydrogen protons (4H+) due to the lone pair of electrons on the outer shell of oxygen. Oxygen exists in nature as di-oxygen (O2) molecules. The oxygen atoms bond with the hydrogen protons, thereby producing atoms of water and leaving the free electrons, thereby generating electricity (4H++4e−+O2→4H++O2+4e−→2H2O+4e−). Other techniques for providing electricity using hydrogen are known as well.
Also in known embodiments, a respective number of individual fuel cells determines a particular output voltage. The cells are electrically connected in series, such that the addition or subtraction of a fuel increases or decreases the output voltage, respectively. As known, the total output voltage is determined by the sum of the each fuel cell's output voltage.
Further, it is known to store hydrogen as a metal hydride, for example, in the crystal lattice of certain metals or metal alloys. As known in the art, an exothermic (heat producing) reaction occurs when hydrogen bonds to the metal (or alloy) to form a metal hydride, and the hydrogen is stored. By applying heat to a metal hydride, the hydrogen is releasable and, thereafter, usable in a fuel cell. Alternatively, hydrogen may be released from the metal hydride using negative air pressure or application of a low electrical current.
Storing hydrogen as a metal hydride would be preferred way to store hydrogen, as it is believed to be safer and easier to handle. Further, a small volume of metal hydride is operable to store a considerable amount of hydrogen and sufficient to provide a considerable amount of fuel to produce electricity. However, a known shortcoming of storing metal hydride for the production of electricity is that the energy storage density per mass is low and, therefore, the storage tanks are considerably heavy. Further, storing hydrogen in metal hydrides generally also requires high pressure to force the hydrogen atoms into the crystalline structure of the metal. A relative lower pressure is necessary to maintain the hydrogen in the metal hydride, typically 450-800 psi, however, even this relatively low storage pressure is too high to be considered safe. Thus high-pressure operation raises the same safety issues discussed above with respect to high-pressure storage of hydrogen gas.
Accordingly, it would be desirable to provide an energy unit that avoids the above problems related to high pressure operation, safety, efficiency and other problems.